From personal experience, this Crobat set is awesome:
Crobat @ Black Sludge
Infiltrator 252HP / 252Spe /4Atk
- Confuse Ray
- Toxic
- Roost
- Brave Bird
As Crobat is freaking fast, Confuse Ray is always first. Then I use Toxic; if the foe manages to strike on Bro even if confused, I Roost...